Production of xylene



Aug. 24, E5 w. LoRz ETAL PRODUCTION OF XYLENE Filed June 2, 1961 UnitedStates VPatent O 3,202,725 PRODUCTEGN OF XYLENE Waldemar Lorz, Yeadon,George Alexander Mills,

Swarthmore, and Harold Shalit, Drexel Hill, Pa., as-

signors to Air Products and Chemicals, Inc., a corporation of DelawareFiled June 2,1961, Ser. No.`114,522 3 Claims. (Cl. 260--67`3.5)

The present invention relates to dehydrocyclization of C8 acyclichydrocarbons and is more particularly concerned with the production ofxylene from C8 acyclic hydrocarbons with special emphasis on theselective production of p-xylene.

The production of aromatic hydrocarbons by dehydrocyclization ofappropriate C6 and higher hydrocarbons is described in prior patents andother technical literature. Itis also known to aromatize selected C8aliphatic hydrocarbons to produce xylenes. Thus, from n-octane there isobtained a mixture of all three isomers of xylene accompanied by ethylbenzene, which mixture predominates in o-xylene. Among the catalystsrecommended for use in these dehydrocyclization processes there ischromium oxide, with or without minor quantities of other metal oxides,supported on gamma alumina.

For selective production of the desired p-xylene isomer bydehy-drocycl'ization -of acyclic C8 hydrocarbons, with only very smallquantities of the other xylene isomers in .the reaction product, it isproposed by F. G. Herington and E. K. Rideal [Proc Roy. Soc. (London)A184, p. 434 (1955)] to -utilize 2,2,4-trimethylpentane :as startingmaterial. Similar processes are described in U.S. Patents 2,785,209 and2,785,210 wherein the suggested initial charge is iso-octane(2,2,4-trimethylpentane) or di-isofbutylene (2,4,t4-trirnethylpentenes),or mixtures of these. These patents describe various catalysts for thisprocess, with lindicated preference :for catalyst comprising to 40%(preferably about y12%) chromium oxide on Igamma. yalumina `andcontaining also minor lamounts of potassium -oxide and cerium oxide.While the aromatics produced in the liquid reaction product reported bythese patents may contain as high as 9598% p-xylene, the totalconversion of the charge starting with isooctane does not exceed about30% and up to about 36% in the case of the mixed trimethylpentenecharge; the yield of p-xylene based on charge being at most less thanabout 12%.

It has now been found, in accordance with the present invention, thatselective conversion of C8 acyclic (parafnic or oleiinic) hydrocarbonscan be obtained at high conversion levels by using specially preparedcatalyst comprising 15% to 25% chromiuml oxide (Cr203) on an aluminabase composed essentially of eta alumina. By the use of such catalyst inthe conversion of isooctane, up to 85% or more of the charge can beconverted, with pxylene yields amounting to about 35% to 45% by weightof vthe charge.

The advantages of the invention can be further enhanced in accordancewith another aspect thereof, by adding to the C8 charge C4 hydrocarbonswhich are simultaneously dehydrogenated. In this manner, not only isthere the advantage of economically converting readily available andrelatively inexpensive C4 parailins to xylenes, but in addition moreeiective temperature control is achieved inasmuch as the presence of theC4 hydrocarbons has a dampening effect on the cyclic temperature swingotherwise encountered in the dehydrocyclization of the C8 hydrocarbonfeed under adiabatic operation, wherein periodic burning of the cokedeposited in the catalyst during the on-stream, period supplies at leastpart of the heat'utilized in the succeeding endothermic hydrocarbonconversion operation. The design of an operative process for beneficialutilization of this feature to augment production of desired C8aromatics is illustrated in the accompanying drawing by way of aschematic flow diagram.

Referring now to the embodiment illustrated in the drawing, there ischarged to the dehydrogenation reactor system 10 a fresh feed 11composed essentially of isobutane and recycle streams 12 and 13containing di-isobutylenes and previously unconverted isobutane. Thedehydrogenation effluent from reactor 10 is sent to a liash drum orother liquid-vapor separator system 14 wherein hydrogen and lowmolecular weight gases (to or through C3) are separated as overhead,while the unvaporized products are withdrawn as liquid in line 15.

The liquid products are sent to a debutanizer 16 preferably in the form.of a fractionating column operated so as to separate out an overheadvapor fraction, withdrawn through line 17, consisting essentially of C3and C., hydrocarbons; the unvaporized higher boiling materials aredischarged through line 18. The overhead gases from the vapor separator14 are sent to an absorber 19, after being compressed to about 50 to 200pounds per square inch. Absorption is effected by means of an aromatichydrocarbon oil introduced into an upper portion of the absorber throughline 20, whereby unabsorbed hydrogen and low molecular weight gases(through C2), which are not absorbed, are withdrawn overhead in line 21,while the rich oil containing absorbed higher molecular weighthydrocarbons is sent by line 22 to stripper 23, operated to separate asoverhead the C3 and C4 hydrocarbons from the absorber oil, the lean oilbeing returned to the absorber 19 through line 20. Thus, the stripper 23may be operated under conditions to discharge as vapor overheadhydrocarbon materials boiling substantially above the initial boilingpoint of the absorber oil. In the typical situation, 'aromatic absorberoils of a boiling range from about F. to about 400 F. can beconveniently employed.

The overhead streams from debutanizer 16 and stripper 23, predominatingin C3 and C4 hydrocarbons, are sent by lines 17 and 24, respectively, toa depropanizer 25, operated to separate out an overhead fraction,discharged through line 26, composed essentially of C3 hydrocarbons richin propylene, while the unvaporized bottoms, composed essentially ofisobutane and isobutene, are sent through line 27 to polymerization(dimerization) in any suitable reactor 28.

Any suitable kno-wn process for dimerization of the isobutenes may beemployed in reactor 2S. For example, the hydrocarbon stream introducedthrough line 27 may be passed over a xed bed of silica alumina catalystat moderate temperatures and pressures and high space rates. Typicaloperations involve temperatures of 300 to 400 F., pressures of 300 to800 pounds per square inch and liquid hourly space rates of .about 3 tol0. Other known dimerization processes employ either phosphoric acidcatalyst or sulfuric acid catalyst at moderate temperatures designed toobtain high yields of desired dimers rich in 2,2,4-trimethyl pentene,and avoiding severity which may tend to promote excessive production ofdimethyl hexenes or 2,3,4- and 2,2,3-trimethyl pentenes. The totalpolymerization product rich in 2,4,4-trimethyl pentene-l and2,4,4-trimethy1 pentene-Z, together with some triisobutylenes in theproduct, is recycled to the dehydrogenation reaction system 10 by meansof line 12 as already indicated.

The bottoms fraction from the debutanizer 16 Vconsists essentially ofC7| hydrocarbons rich in aromatics. These are fractionated in column 29to separate out as overhead vapors hydrocarbons boiling up to about 222F. or

slightly above, but short of the boiling point of toluene (about 230 R).The overhead fraction, which is compo-sed chiefly of unconverteddiisobutylene together with a some higher liquid polymer, is recycled byline 13 to the dehydrogenation reactor as already indicated, The buttomsfraction from column 29 is sent by line 31 to fractionating column 32wherein toluene and lower boiling hydrocarbons are withdrawn as vaporoverhead in line 33, thereby recovering at 34 the C8 aromatichydrocarbons, which will contain 95% or higher p-xylene, the remainderbeing almost entirely isomers thereof.

For the combined dehydrogenation operation carried out in reactor 10,wherein the fresh charge is composed essentially of fresh isobutanewhich is dehydrogenated to isobutylene while recycled dimer issimultaneously converted to xylene, preferred operating conditionsinclude temperatures in the range of 1000 to 1100 F., and low pressuresranging from about 5 inches or mercury absolute to atmospheric (30 in.Hg). Space rates may be in the range of 0.5 to 2 volumes per hour.

When the dehydrocyclization process is operated, with iso-octane ordiisobutylene as fresh charge, for production of an aromatics productconsisting essentially of p-xylene, somewhat lower operating severitycan be employed; thus temperatures in .the range of about 950 to 1050 F.can be utilized, preferably in the range of 975 to 1025 F. for bestoverall results from the standpoint of achieving high conversion levelswithout excessive production of coke and light hydrocarbon gases. Whileatmospheric or even slightly elevated pressure can be used, it isadvantageous even here to operate at subatmospheric pressure so as tofavor 1'C4 olens rather than parains in the by-products. The isobutaneand iso C4 olens produced in this process can be recovered andseparated, if desired, or these can be directly recycled 'as such,joining the fresh C3 charge fed to dehydrocyclization. The presence ofrecycled isobutylene may serve to suppress splitting of the C8 feed tosome extent, and in addition thereto some part of the z'C4 parains andolefins may be directly converted to xylene by a gas reversion typemechanism taking place in the dehydrocyclization reactor, as illustratedby the reactions:

Operating at the indicated pressure, the feed rate of the C8 hydrocarbonmay lie in the range of 0.2 to 2.0 volumes per hour per volume ofcatalyst (Ll-ISV) and is preferably selected so that at the temperatureand pressure employed at least 50% and preferably greater conversion ofthe C8 charge is obtained. If the iC4 hydrocarbons are recycled-asparans, olens or mixtures of these-the same temperatures and pressure ingeneral may be employed as when fresh C8 feed only is used, but thetotal hydrocarbon space rate should be accordingly adjusted to obtainoperating severity consistent with a minimum of 50% conversion of C8hydrocarbons.

As indicated above, an important feature of the invention is theparticular catalyst used. Eta alumina, which constitutes the whole ormajor part of the support or carrier for the active catalytic component,can be produced by heating beta alumina trihydrate (Bayerite) attemperature in the range of about 600-1400" F. Alumina beta trihydratecan be obtained by various methods known to the art; one such methodinvolves the hydrolysis of aluminum alcoholate with ammonium hydroxide.Other methods involve the controlled aging of aluminum hydroxide gels.Beta alumina trihydrate in substantially pure form (97-{-%) is nowavailable commercially; also available are marketed mixtures of hydratedalumina contining 75% or more beta alumina trihydrate in associationwith alpha trihydrate (Gibbsite) or with alpha monohydrate (boehmite) orsometimes with both of these. Calcination (dehydration) of the alphatrihydrate leads to the production of typical gamma form of alumina,heretofore known to the art, as activated alumina. In calcining aluminahydrate mixtures containing beta trihydrate with these alpha hydrates,there is obtained a corresponding calcined product comprising eta andgamma forms of alumina. The catalysts used in the practice of thepresent invention are prepared by impregnation of a dehydrated aluminabase obtained from hydrated alumina containing at least 60% Iandpreferably in excess of 75 beta trihydrate. The dehydrated aluminaproduct is subjected to further heat treatment to adjust the surfacearea to the range of about 100 to 300 square meters per gram and thenimpregnated with chromic acid or other decomposable soluble chromiumcompound to incorporate 15 to 25% Cr2O3 by weight of the finishedcatalyst, after which the impregnated product is dried and calcined. Thecalcined chrome-alumina catalyst has a surface area of about 50-150square meters per gram.

The preferred catalysts used in practice of the invention are thosewhich contain at least 0.6% and preferably 0.8 to 1.5% by weight alkalimetal ion calculated at Na2O; ie., the corresponding potassium compoundused in the same molecular proportions would entail the weight range ofat least 0.9% K2O, preferably 1.2 to 2.3% KZO by weight of the catalyst.Commercial hydrated alumina compositions composed of or predominating inbeta trihydrate vary in alkali metal content from about less than 0.1%NazO to generally about 0.6% NaZO. To incorporate additional alkalimetal ion there may be admixed with the aqueous paste of the aluminahydrate employed in formation of granules or pellets, sodium bentoniteor sodium hydroxide in an amount sucient to provide the desired alkalimetal content in the finished catalyst. On the other hand, the sodium orother alkali metal may be incorporated in the pelleted material byinclusion in the solution employed for chrome impregnation. Thus, thedesired amount of Na2O may be furnished by adding a small amount ofsodium chromate to the chromic acid or the chromic acid solution may bepartly neutralized by sodium hydroxide. The presence of the indicatedamount of alkali metal in the catalyst is believed to enhance theselectivity of the catalyst for dehydrocyclization operations whilereducing the degree of acid-catalyzed side reactions includingisomerization, polymerization, and carbon-carbon scission.

EXAMPLE I The preferred catalyst employed in practice of the inventionis prepared in the manner described below:

Commercial alumina beta trihydrate (96-{-% bayerite) was thoroughlyadmixed by mulling with aqueous nitric acid employing 0.09 part nitricacid (1.42 S.G.) and 0.108 water by weight of the alumina trihydrate.The acid mix after standing overnight was extruded through a die plateand the strands cut to form 2.4 mm. pellets. The pellets were dried at240 F. and dehydrated iu air at about G-900 F. (surface area=367m.2/g.). The dehydrated pellets were then subjected to surface areaadjustment by steaming (100% H2O) for 2 hours at 900 F. (surfacearea=170190 m.2/g.).

The area-adjusted pellets were impregnated by soaking in a chromic acidsolution, employing 1 liter of the solution for each kilogram ofpellets. The chromic acid solution was prepared by dissolving Cr03 inwater to form a solution of 1.420 specific gravity (6D/60 F.) containingabout 550 grams CrO3 per liter of solution, in which there was alsodissolved solid sodium hydroxide furnishing 41.8 grams NaOH per liter.After 2 hours soaking, the excess liquid was decanted from the pellets.The drained pellets were dried in air at 250 F., then heat treated for 4hours at 1400 F., in an atmosphere of 20% steam and 80% air. Thefinished pellets analyzed 1.09% NazO by weight.

The catalyst pellets had the following approximate composition:

EXAMPLE 1I Table 1 ISOOCTANE RUNS Run No 1 2 3 4 5 6 950 1 000 1, 000 1,000 1, 000 1, 000 0.25 0 25 1.0 1.0 1. 5 0.5 l 3 3 Products Wt. percentchg.

(no loss basis): a

77. 4 63. 3 86. 9 79. 4 65. 8 69. 1 22. 4 36. 4 11. 4 18. 7 3l. 7 28. 60.2 0.3 1.7 1.9 2.5 2.3 Conversion,

chg.x 35; 7 75. 2 53. 9 69. 1 83. 7 81. 7 Sellec., wt. percent chg 3438. 5 71 64.7 53. 1 56.1 Yleld/pass, wt. percent .chg 12. 2 28. 9V 38. 344. 7 44. 4V 45. 8 Liquid anal., wt. perl f cent:

lsopctane 77. 4 28. 36 26. 1 17. 4 18. 6 Diisobutylene.. 5. 7 10.0 17. 112. 9 7. 3 7. 9 p-Xylene 15. 7 45. 7 43. 7 56. 3 67. 6 66. [J GasAnalysis, wt. percent:

Hydrogen 4. 7 5. 4 20. 5 14. 3 8.8 9. 4 Isobutane. 60. 8 63.8 44. 7 48.4 45. 2 49. 2 lTotal butenes 16. 7 19. 5 17. 7 24. 4 23. 0 23. 3

1 Conversion is based on and diisobutylene.

2 Utilization of at least a portion of the butenes as recycle materialafter suitable processing as by dimerization will increase theselectivity products in the effluent other than isooctane value.

Table 2 DIISOBUTYLENE RUNS Run No 7 8 9 10 Oper. Cond.:

Temp 1, 000 1, 000 1, 000 1, 000

Hz/oil mol 3 1. 5 Products, wt. percent chg. (no loss basis):

Liquid 60 66. 7 61. 3 66. 7

Gas 35. 6 32. 9 87.3 31. 3

Coke 4. 4 0. 8 1. 4 2. 0 Conversion, wt. percent chg.- 94 92. 4 92 89. 4Selectivlty, wt. percent chg 35. 7 41 37. 2 45. 7 Yield/pass, wt.percent chg 33. 6 37 9 34. 2 40. 9 Liquid anal., wt. percent:

Diisobutylene 11. 3 11. 4 13. 1 15.9

p-Xylene 56 56. 8 55. 9 61.2 Gas analysis, wt.

Hydrogen- 0. 5 1. 6 1. 6 4. 7

Isobutane 76. 2 73. 4 64. 1 50. 8

Total buteues 14. 9 11. 8 22. 7 29. 8

It will be seen from the foregoing tables that under conditions ofsuliicient severity to obtain 50% or greater conversion of the charge,once-through yields of -45% p-xylene are obtained by weight of charge.Moreover, the aromatics fraction in the liquid effluent is of highpurity in p-xylene and relatively free of the other C8 aromatic isomers.The isooctane and diisobutylene in the liquid product can, of course,`be recycled to dehydrocyclization for conversion to additional p-xylene.Considering such recycle operation, the highest ultimate yields would beobtainedunder conditions of Runs 3 and 4, carried out at a severitylevel giving about 50-70% per pass conversion of C8 charge. At higherconversion level, there is a corresponding loss in selectivity. Theaddition of hydrogen appears to lower the once-through yield to someextent, but on the other hand may tend to reduce the quantity of cokedeposited.

' EXAMPLE n1 A series of runs were made over catalyst similar to that ofthe previous example at the conditions given below to determine theeffect of varying the ratio of isobutane/di- 6 isobutylen'e in' thefeed. The results are table below:

reported in the T able 3 Run N0 1 2 3 4 5 6 Temp., F 1, 050 l, 050 1,050 1, 100 1, 100 1, 100 Pressure, mm. Hg 400 400 400 400 120 120 Spacerate (GHSV l) 200 300 400 400 800 400 Isobutane to DIB mol ratio 0.9 1.9 2.8 2. 8 6. 4 2. 8

Data Based On: Isobutane and YDIB-Isobutylene and pXylene Wt. percentchg.:

Conversion 74. 2 66. 7 62. 4 74. 8 44. 3 60. 7 Selectivity 80. 3 85. 883. 3 77. 3 79. 9 76. 9 Yield/pass 59. 6 57 52 57. 8 35. 4 46. 7

Data Based On: Isobutane pXylene Wt. percent chg.:

Conversion 37. 8 26. 7 Y 23. 9 29. 4 16. 8 25. 4 selectivity- 61. 6 64.4 56. 6 42. 2 47 44. 9

Yield/pass... 23. 3 17. 2 13. 5 12. 4 7. 9 11.4

1 GHSV=Volume vapor per hour per volume catalyst.

From these runs it appears that desired product 'balance is obtained atisobutane/DIB rnol ratios of 2 to 3; approximate equilibrium conditions`are`obtained when the mol ratio of isobutane/isobutylene in the chargelies in the range of 2 to 4. i

`In the illustrated embodiment of the invention diisobutylene isrecycled to the reactor in which dehydrogenation of isobutane isalsoeiected. If desired, alternatively, separate reactors may be provided,respectively, for dehydrogenation of the isobutane and Vfor cyclizationof the diisobutylene, wherein the latter may be operated at somewhatlower severity including lower temperature and higher pressureapproaching atmospheric. In such operation, any isobutylene that is notpolymerized at Z8 would Obviously many modifications and variations ofthe invention as hereinbefore set forth may be made Without departingfrom the spirit and scope thereof, and therefore only such limitationsshould be imposed as are indicated in the appended claims.

What is claimed is:

1. The method for production of p-xylene which comprises: feeding to acatalytic dehydrogenation zone mixed hydrocarbon streams, including atleast one recycled products stream comprising diisobutylene, and isoC4hydrocarbons comprising isobutane, the ratio of isoC4 hydrocarbons todiisobutylene ibeing within the range from about 2:1 to about 3:1;contacting said mixed hydrocarbon streams in said dehydrogenation zonewith chromealumina catalyst comprising 15 to 25% chromium oxide,determined as CrZOB, and alkali metal in an amount equivalentto at least0.6% by weight Na20 on alumina carrier, said catalyst having beenobtained by dehydratng beta alumina trihydrate to produce sorptivealumina having a large surface area, lowering the surface area to withinthe range from to 300 m.2/ g. by treatment with hot steam, impregnatingthe surface reduced alumina, and heating the impregnated eta alumina,said contacting being effected at a temperature in the range of 1000 to1100 F. and pressure in the range of 5-30 inches Hg absolute, and at aspace rate correlated therewith to obtain at least 50% conversion of C8hydrocarbons in the charge with resulting production of productsincluding p-xylene and isobutylene; separatingfrom the resultingproducts hydrogen and hydrocarbons up to C3; further separating from thereaction products isoC., hydrocarbons to provide an aromatic residualfraction; subjecting said separated isoC4 hydrocarbons to dimerizationin a separate reaction zone to obtain diisobutylene; admixing theobtained diisobutylene with the fresh isobutane charged aromaticresidual fraction a Xylene cut highly concentrated in p-xylene.

2. The method producing a hydrocarbon product of high p-Xylene contentwhich comprises feeding to a dehydrogenation zone a hydrocarbon mixtureof isobutane and diisobutylene under conditions effecting simultaneouscyclization of said diisobutylene and dehydrogenation of said isobutane,said condi-tions including contact of said hydrocarbon mixture to obtainat least 50% conversion of C8 hydrocarbons and the contacting of saidhydrocarbon mixture with catalyst prepared by dehydrating an aluminahydrate composition containing at least 60% beta trihydrate, adjustingthe surface areaby treatment with hot steam to a surface area in therange of 100 to 300 m.2/ g., impregnating the surface reduced alumina,and heating the impregnated alumina to prepare a chromia on eta aluminacomprising 15 to 25% Cr203, and said conditions including temperature inthe range of 1000 to 1100 F., and at a pressure in the range of fromabout 5 inches of mercury absolute pressure to about 30 inches ofmercury absolute pressure.

3. The method for preparation of p- Xylene which cornprises thefollowing steps:

l (a) feeding to a catalytic dehydrogenation zone a fresh hydrocarbonchargeconsisting essentially of isobutane,

(b) feeding to said dehydrogenation zone diisobutylene, v (c)dehydrogenating said fresh hydrocarbon charge in the presence of saiddiisobutylene to produce isobutylene therefrom while converting part ofsaid diisobutylene to Xylene, said dehydrogenation zone being attemperature inthe range of 1000 to 1100" F.

and at subatmospheric pressure within the range fromv about 5 inches ofmercury absolute to about 30 inches of mercury absolute and containing abed of l catalyst comprising 15 to 25% Cr2O3 on an alumina basecomprising eta alumina, said base having been obtained by dehydration ofa hydrated alumina consisting essentially of beta alumina trihydrate,

(d) withdrawing the reaction products from said dehydrogenation zone andremovingrtherefrom hydrogen and light hydrocarbons through C3 leaving a,

(e) removing from said C4| hydrocarbon product a fraction concentratedin iC4 hydrocarbons, including isobutylene, leaving anaromatics-containing hydrocarbon fraction,

(f) separating unconverted diisobutylene from said aromatics-containingfraction and recycling said diisobutylene to said dehydrogenation zone,

g) further fractionating the aromatics-containing fraction, afterremoval of diisobutylene therefrom, to separate out toluene and lowerboiling hydrocarbons, thereby recovering a C8 aromatic fractionconcentrated in p-xylene,

(h) polymerizing the isobutylene from step (e) to produce additionaldiisobutylene, and

' (i) feeding the polymerization product from step (h) to thedehydrogenation zone.

References Cited by the Examiner UNITED STATES PATENTS 2,734,022 2/56Kimberlin et al. 208-136 2,785,209 3/ 57 Schmetterling et al. 260-673.52,785,210 3/57 Schmetterling et al. 260-673.5 2,796,326 6/57 Kimberlinetal. 20S-138 XR 2,863,826 12/58 Holcomb et al. 260-673.5 XR 2,941,016 6/60 Schmetterling et al. 260-673.5 2,962,536 11/60 Pitts 260-673.52,985,693 5/61 Probst et al. 260673.5 3,064,062 11/62 Lorz et al.260-683.3

ALPHONSO D. SULLIVAN, Primary Examiner.

MILTON STERMAN, Examiner.

1. THE METHOD FOR PRODUCTION OF P-XYLENE WHICH COMPRISES: FEEDING TO A CATALYTIC DEHYDROGENATION ZONE MIXED HYDROCARBON STREAMS, INCLUDING AT LEAST ONE RECYCLED PRODUCTS STREAM COMPRISING DIISOBUTYLENE, AND ISOC4 HYDROCARBONS COMPRISING ISOBUTANE, THE RATIO OF ISOC4 HYDROCARBONS TO DIISOBUTYLENE BEING WITHIN THE RANGE FROM ABOUT 2:1 TO ABOUT 3:1; CONTACTING SAID MIXED HYDROCARBON STREAMS IN SAID DEHYDROGENATION ZONE WITH CHROMEALUMINA CATALYST COMPRISING 15 TO 25% CHROMIUM OXIDE, DETERMINED AS CR2/3, AND ALKALI METAL IN AN AMOUNT EQUIVALENT TO AT LEAST 0.6% BY WEIGHT NA2O ON ALUMINA CARRIER, SAID CATALYST HAVING BEEN OBTAINED BY DEHYDRATING BETA ALUMINA TRIHYDRATE TO PRODUCE SORPTIVE ALUMINA HAVING A LARGE SURFACE AREA, LOWERING THE SURFACE AREA TO WITHIN THE RANGE FROM 100 TO 300 AM.2/G. BY TREATMENT WITH HOT STEAM, IMPREGNATING THE SURFACE REDUCED ALUMINA, AND HEATING THE IMPREGNATED ETA ALUMINA, SAID CONTACTING BEING EFFECTED AT A TEMPERATURE IN THE RANGE OF 1000 TO 1100*F. AND PRESSURE IN THE RANGE OF 5-30 INCHES HG ABSOLUTE, AND AT A SPACE RATE CORRELATED THEREWITH TO OBTAIN AT LEAST 50, CONVERSION OF C8 HYDROCARBONS IN THE CHARGE WITH RESULTING PRODUCTION OF PRODUCTS INCLUDING 